Create count-words-obtained-after-adding-a-letter.py

Author: kamyu104

Python/count-words-obtained-after-adding-a-letter.py

@@ -0,0 +1,19 @@
+# Time:  O(n)
+# Space: O(n)
+
+class Solution(object):
+    def wordCount(self, startWords, targetWords):
+        """
+        :type startWords: List[str]
+        :type targetWords: List[str]
+        :rtype: int
+        """
+        def bitmask(w):
+            return reduce(lambda x, y: x|y, (1 << (ord(c)-ord('a')) for i, c in enumerate(w)))
+
+        lookup = set(bitmask(w) for w in startWords)
+        result = 0 
+        for w in targetWords: 
+            mask = bitmask(w)
+            result += any(mask ^ (1 << ord(c)-ord('a')) in lookup for c in w)
+        return result